Sound is a fundamental part of all of
our lives. It helps us to communicate, to judge distances, to
identify earthquakes. But what is sound? Sound is a longitudinal
wave. That means it travels much as a rubber band or slinky, coming
together at one point and expanding at another. In other words, the
wave direction is parallel to the medium through which it is
traveling.

Sound travels at different speeds and
intensities through air, water, and solids. This is due to the
closeness of particles in each of these mediums. So, since solids are
the most compact (the ones with the closest particles), sound travels
fastest and more intensely through this, followed by water, and then
air.

Frequency is another important aspect of
sound. The more frequent the sound wave cycles through the medium,
the higher pitched it is. It is the frequency that gives us different
musical notes. Frequency is often raised by shortening the medium
through which the sound is traveling. That is why shorter strings
sound at a higher pitch than longer ones.

Sound waves themselves always travel in
circular rings. This causes what is known as diffraction. Some waves
bend around corners and through openings, and a new series of waves
start on the other side. This results in patterns that are similar to
these that follow:

Methodology:

XPERIMENT 1: SOUND IN DIFFERENT
MEDIUMS

Part 1: Sound in Water

1. Take the tuning fork and strike solidly
against a hard surface.

2. Take the vibrating tuning fork and place
tip into plastic container filled three-quarters of the way with
water.

3. Observe the waves as they travel through
the water. These are the sound waves.

Part 2: Sound in Solids

4. Grab the prongs of the tuning fork so
that they stop vibrating.

5. Strike tuning fork once again against a
hard surface.

6. Have students place their ears against a
counter top or desk, and rest the vibrating tuning fork on this
surface.

Part 3: Sound through Air

7. Strike the tuning fork again.

8. Place tuning fork 6 to 8 inches away from
the students' ears.

9. Observe the differences between how the
sound waves sounded like in the solid and air mediums.

EXPERIMENT 2: FREQUENCY

Different pitches in sound come from various
frequencies of the sound waves themselves. In this experiment, we
will observe the results of these various frequencies.

Part 1: Musical Drinking Glasses

1. Take the drinking glasses and fill each
with a different amount of water.

2. Allow students to strike the glasses with
the knife.

3. Listen to the varying pitches as the
glasses go from mostly empty to almost full.

Part 2: Your own Instrument

4. Take the pieces of cardboard and fold up
both ends. One end should be about half the size of the
other.

5. On the shorter side, make various slits
on the top edge of the fold.

6. Take the longer side and fold it again.
On the two open sides, make various slits equally spaced.

7. Take the fishing wire and tie a knot in
the end of each of the pieces.

8. Stretch the pieces from each of the slits
in the shorter end to that of the longer end.

9. Tie off the other end, so you have
something slightly resembling a guitar.

10. Let the students pluck the strings and
notice the difference in sound each string makes.

EXPERIMENT 3: DIFFRACTION

1. Take the divider. If there is not a cut
in the center of it, make one.

2. Place the divider in the plastic
container. Make sure it fits securely inside.

3. Fill the plastic container with the
divider in it to just above where the cut ends.

4. Take the tuning fork and strike it
against a solid object.

5. Place one prong in the plastic container
as far away from the divider as possible.

6. Watch as the waves expand from the point
of contact and hit the divider.

7. Notice that a few of the waves travel
beyond the divider by means of the cut.

8. This is the phenomenon of diffraction:
the spreading of sound waves beyond the edges of a
divider.